Maintain backwards compatiblity, deprecate flag

Author: AgeManning

beacon_node/src/cli.rs

@@ -1268,5 +1268,11 @@ pub fn cli_app<'a, 'b>() -> App<'a, 'b> {
                 .default_value("64")
                 .takes_value(true)
         )
+        .arg(
+            Arg::with_name("disable-duplicate-warn-logs")
+                .long("disable-duplicate-warn-logs")
+                .help("This flag is deprecated and has no effect.")
+                .takes_value(false)
+        )
         .group(ArgGroup::with_name("enable_http").args(&["http", "gui", "staking"]).multiple(true))
 }

lighthouse/tests/beacon_node.rs

@@ -2584,3 +2584,22 @@ fn genesis_state_url_value() {
             assert_eq!(config.genesis_state_url_timeout, Duration::from_secs(42));
         });
 }
+
+#[test]
+fn disable_duplicate_warn_logs_default() {
+    CommandLineTest::new()
+        .run_with_zero_port()
+        .with_config(|config| {
+            assert_eq!(config.network.disable_duplicate_warn_logs, false);
+        });
+}
+
+#[test]
+fn disable_duplicate_warn_logs() {
+    CommandLineTest::new()
+        .flag("disable-duplicate-warn-logs", None)
+        .run_with_zero_port()
+        .with_config(|config| {
+            assert_eq!(config.network.disable_duplicate_warn_logs, true);
+        });
+}